GHA: Include the subdir in tarball

[tleedjarv]

Inspired by #1118, I think this was actually a bug in the original CI script, which was then also assumed by the _compat builds. This was very simple to change, so why not go for it.

[gdt]

Is the idea that the SHA1 of the sources is in the tarball name? I think that's important to reduce confusion about which tarball is which later, and I'm pretty sure that's what you would intend. Looks like the commit is 46dbd65cdbcc60f68cfbb6798565cf3629bacabe. But an artifact is https://github.com/bcpierce00/unison/suites/34502718465/artifacts/2605140450 or at least that's the unhelpful link, and it downloads as unison-git_81cd90ca-ubuntu-x86_64.tar.gz___ocaml-4.14.x.ubuntu_compat-publish.zip with that hash inside. That looks like a commit hash, but I can't find it (I have your repo as a remote, so it's been fetched, and git log 46db shows me the commit).

[tleedjarv]

That's right, the dir name is the same as tarball name (sans .tar.gz).

With an unmerged PR you get a different hash because GHA does a merge for the build (just look at the logs at the checkout step, for example: https://github.com/bcpierce00/unison/pull/1123/checks#step:3:61). This is completely unrelated to this PR.

[gdt]

That's quite the GHA bug, making it hard to tie unmerged PR test artifacts back, but it's definitely not a bar to this fix.

[tleedjarv]

That's quite the GHA bug, making it hard to tie unmerged PR test artifacts back, but it's definitely not a bar to this fix.

I think there's a way around it (not sure why it's not the default). I'll try it out and open another PR.